Can't make a search in Windows Phone

Hi, I'm just starting with Linq to Twitter. I'm developing an app where I need to search tweets for location, but I've found it to be different in W8 than in Windows Phone, and I haven't been able to do it.

The thing here is that I'm not sure if it's due to the AsyncCallback, if I parse asyncResponse and assign it to a variable, it's always null.

Thanks in advance!

Edit: If it's an authentication problem, I don't want to use web auth, like in "MetroSearchDemo" Sample, is that possible? If not, how can I send a callback URL? I only found it on WinRtAuthorizer, not available on WP.